ON-BOARD DIAG (OBD) SYSTEM IMPROVE. (RE-FLASH CALIB.). GMC Truck GMC C Pickup

SUBJECT: ON-BOARD DIAGNOSTIC (OBD) SYSTEM IMPROVEMENTS (RE-FLASH CALIBRATION)

MODELS: 1997 CHEVROLET AND GMC C/K, P TRUCKS WITH 5.7L V8 ENGINE (VIN R--RPO L31) AND AUTOMATIC TRANSMISSION (MT1)

VIN BREAKPOINTS:

CHEVROLET C/K FLINT VF000030 THRU VF021979 CHEVROLET C/K PONTIAC EAST VE100003 THRU VE186674 CHEVROLET C/K FT. WAYNE VZ104227 THRU VZ169887 CHEVROLET P DETROIT V3300044 THRU V3308991

GMC C/K FLINT VF001421 THRU VF018506 GMC C/K PONTIAC EAST VE500019 THRU VE532436 GMC C/K FT. WAYNE VZ500699 THRU VZ522379 GMC P DETROIT V3500013 THRU V3501180

WHILE THE SUBJECT VEHICLES HAVE BEEN CERTIFIED AS COMPLYING WITH THE APPLICABLE U.S. ENVIRONMENTAL PROTECTION AGENCY (EPA) AND CALIFORNIA AIR RESOURCES BOARD (CARB) ON-BOARD DIAGNOSTIC (OBD) REQUIREMENTS, WE HAVE IDENTIFIED AN OBD SYSTEM IMPROVEMENT THAT SHOULD BE IMPLEMENTED WHENEVER PRACTICAL.

CONDITION:

ENGINE MISFIRE DIAGNOSTICS HAVE BEEN INADVERTENTLY DISABLED.

CAUSE:

SOME VEHICLES WERE RELEASED WITH SOFTWARE WHICH INADVERTENTLY DISABLED THE MISFIRE DIAGNOSTICS.

CORRECTION:

USE A TECH II TO VERIFY WHAT SOFTWARE IS PROGRAMMED INTO THE VEHICLE VCM. IF THE IMPROVED SOFTWARE HAS NOT BEEN INSTALLED, REPROGRAM/ RE-FLASH WITH THE UPDATED SOFTWARE. REFER TO THE LISTED TABLE FOR THE APPROPRIATE CALIBRATION CHANGES.

MODEL EMISSION TYPE NEW CAL OLD CAL

C/K NA4/NB6-KL6 16256293 16243426 P NB6 16256303 16243457

IMPORTANT: INFORM CUSTOMERS THAT THIS WORK IS BEING PERFORMED ON THEIR VEHICLES TO IMPROVE ON-BOARD DIAGNOSTIC SYSTEM OPERATION AND DOES NOT AFFECT VEHICLE DURABILITY, RELIABILITY, OR PERFORMANCE.

CALIBRATION INFORMATION:

THE CALIBRATIONS LISTED ARE FLASH CALIBRATIONS AND NOT AVAILABLE FROM GMSPO. SERVICE FLASH CALIBRATIONS ARE AVAILABLE STARTING WITH THE 1997 NUMBER 5 CD ROM.

WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION: J-6355 LABOR TIME: 0.4 HRS.

IMPORTANT: THIS LABOR OPERATION IS COVERED UNDER EITHER THE FEDERAL OR CALIFORNIA EMISSION CONTROL SYSTEM WARRANTY (WHICH- EVER APPLIES) OR THE BUMPER-TO-BUMPER COVERAGE IN THE NEW VEHICLE LIMITED WARRANTY. THE WARRANTY WITH THE BROADEST COVERAGE APPLIES.

FIGURES: 0 ATTACHMENTS: 0

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.